How to Read Betting Odds
American, decimal, and what the vig is actually charging you.
Odds are just probability wearing a price tag. The same line shows up in two common formats.
American odds
A favorite shows a negative number — -150 means risk $150 to win $100. An underdog shows a positive number — +130 means risk $100 to win $130. The bigger the number, the bigger the mismatch.
Decimal odds
Decimal odds are your total return per $1 staked. 2.50 returns $2.50 (your $1 back plus $1.50). To convert: a +130 underdog is 2.30; a -150 favorite is 1.67.
The vig (juice) — why both sides aren't even
A coin flip should pay +100 on each side. Instead you'll see -110 / -110. That extra is the vig — the book's margin. Add the two implied probabilities and they sum to more than 100%; the overround is the hold. Removing it ("de-vigging") gives the book's true line — which is exactly what our Fair Value tool does before comparing to the market.
Why it matters
Two books rarely price a game identically. Taking +130 instead of +120, or -105 instead of -115, is free money over time. That's line shopping — and the single most reliable edge a casual bettor can capture.